2026ApJ...999..114K

The cusp-core problem remains a challenge to the ΛCDM model, since dwarf galaxies often exhibit flat central density cores rather than the steep cusps (ρ ∝ r^–1) predicted by collisionless N-body simulations. We model the dark-matter-dominated dwarf irregular galaxy DDO 168 within the Bose-Einstein condensate (BEC) or fuzzy dark matter (FDM) framework, in which ultralight bosons form a solitonic core governed by the Gross-Pitaevskii-Poisson (GPP) equations, with the soliton mass-radius relation enforced. We numerically validate the ground-state solution of the GPP system as a consistency check and fit the inner rotation curve of DDO 168 using SPARC data. Within this framework, the data are consistent with an axion mass $m=(1.{3}_{-0.2}^{+0.3})\times 1{0}^{-23}\,{\rm{eV}}$, and yield a solitonic core with characteristic radius ${R}_{c}=2.4{0}_{-0.24}^{+0.22}\,{\rm{kpc}}$, enclosing a mass M(<2.47 kpc) ≃ (1.5 ± 0.2) × 10⁹M_⊙. The observed flat inner rotation curve is reproduced and the presence of a weak H I bar is compatible with multigigayear survival timescales, consistent with reduced Chandrasekhar dynamical friction in a shallow central potential. These results demonstrate that the BEC/FDM framework provides an internally consistent description of DDO 168, simultaneously reproducing the observed rotation curve, alleviating the cusp-core tension, and allowing long-lived weak bars under conservative dynamical assumptions.